1. Field of the Invention
This invention relates to an adsorber temperature-estimating device for internal combustion engines, which estimates the temperature of an adsorber which is arranged in the exhaust system of the engine, for adsorbing an unburnt gas component present in exhaust gases, and also to an exhaust gas-purifying system for internal combustion engines, using the adsorber temperature-estimating device.
2. Prior Art
An exhaust gas-purifying system for internal combustion engines, which is equipped with an adsorber arranged in the exhaust system of the engine, for adsorbing an unburnt gas component (HC) contained in exhaust gases from the engine, has been conventionally proposed, for example, by Japanese Provisional Patent Publication (Kokai) No. 5-149130, wherein the temperature of an adsorbent accommodated in the adsorber is detected by a sensor, and the air-fuel ratio of exhaust gases or the amount of secondary air to be supplied to the exhaust system is controlled based on the detected temperature of the adsorbent as well as an output from an air-fuel ratio sensor arranged in the exhaust system, to thereby maximize the conversion efficiency of a catalytic converter arranged in the exhaust system and hence improve exhaust emission characteristics of the engine. Adsorbers of this kind including the one of the above proposed system, is used in the following manner: When the engine is in a cold condition such as at the start thereof, a large amount of unburnt exhaust component (HC) in exhaust gases is adsorbed and collected by the adsorber, while when the exhaust gas temperature rises subsequently, the HC is desorbed from the adsorber and delivered to the catalytic converter downstream of the adsorber, where the HC as well as CO and NOx in the exhaust gases are purified.
In the above proposed conventional system, however, since the temperature of the adsorbent or adsorber is detected by the sensor, the detected temperature unfavorably varies with a variation range of about .+-.25.degree. C. due to variations in characteristics of the sensor. Besides, the use of the sensor forms a factor for an increased manufacturing cost of the system.